Process for treating fruits



Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE No Drawing.Application July 28, 1933, Serial No. 682,665

20 Claims. (Cl. 99-103) My invention relates to the art of artificiallyripening fruits and with the coloring thereof, and deals moreparticularly with the ripening of the so-called citrous fruits.

This is a continuation in part of my application, Serial No.349,912,,filed March 25, 1929, entitled Process for ripening citrousfruits.

Since time immemorial various processes have been used for theartificial coloring and ripening of fruits in storage. The Chinese haveexposed the fruit to the gases obtained from burning incense. In morerecent times in this country the sweating process has been used,involving the storage of fruits and vegetables at warm temperatureswhich speeds .up the chemical changes taking place therein and resultsin a fruit or vegetable having many of the same characteristics as thenaturally ripened product. It was found, however, that this ripeningprocess could be materially accelerated by exposing the fruit to variousgases such as the exhaust from, internal combustion engines and thewaste gases from blue flame kerosene burners. Upon investigation it wasfound that the efficacy of the gases for this purpose was due in a largemeasure to, the presence of unsaturated gaseous hydrocarbon compoundsand principally to ethylene, perhaps because of its greaterconcentration in these waste gases.

As a result of this discovery ethylene gas mixed with air in lowconcentrations was used for the production of desirable coloring inimmature lemons. Shortly thereafter it was discovered that this processwas also applicable to the ripening of other fruits and vegetables moreespecially bananas, tomatoes and celery. The use of ethylenegas has,however, heretofore been impotent in ripening immature and green citrousfruits. Attempts to ripen these fruits with ethylene have resulted inthe production of best of fruit having the appearance of ripeness butretaining all of the acidity and low sugar content of the green fruit.The fruit was colored but no ripening change took place in the body ofthe fruit.

Various citrous fruit producing States, principally the State ofFlorida, have enacted laws regulating the shipment of fruits therefromin orderto establish a minimum quality and maintain the fruit standardof the State. Because of these restrictions unscrupulous fruit dealershave imported green and immature fruit from Puerto Rico, Cuba, and othersouthern countries by way of ports where no such limitations exist as aresult of which the fruit dealers of the restricted areas have beendeprived of a portion of their market. The dealers are thus permitted toimport green and immature fruit and place them upon the market beforedomestic fruit has matured. A secondary effect of this activity is thecreation of a prejudice against the species of fruit by those whoinadvertently buy the immature product. There has heretofore been noknown method by which immature fruits may be ripened sufficiently tofulfill the requirements of the citrous fruit laws. The benefits to bederived from a process of. this kind will be apparent. Citrous fruits.reach their full size before they are mature or fulfill therequirements of the citrous fruit laws in Florida, and therefore, if thesugar content could be increased by artificial means there would be asaving of approximately loaded, the fruit drops and this means a loss.This I fruit could be treated and saved as well as normal fruit andfruit which does not seem to be ripening properly.

Ethylene has been used in the past for coloring citrous fruits, themaximum concentration being limited to one part of ethylene to 5000parts of air. position of the fruit, but only speeds up thedecomposition of the chlorophyll in the peel. It has also been used forthe ripening of certain fruits and vegetables which have largecarbohydrate reserves and thin skins; such as bananas, tomatoes andcelery. The concentration in the latter cases is limited to about onepart of gas to 1000 parts of air. Greater concentration is not generallyfavorable for ripening these fruits. Instructions relative to thisprocess have usually contained specific instructions to the operator notto employ a greater concentration than one part to 1000, since greaterconcentrations'have a detrimental effect upon the fruit.

An important object of my invention is the provision of a process forripening immature and green citrous fruits in storage. A still furtherobject is the provision of a process for accelerating the action of agas of the ethylene series.

Another object of the invention is the provision of an improved methodfor the coloring of citrous fruits.

I have also aimed to provide a novel composition for the treatment offruit to accelerate the coloring and the ripening thereof.

I have also aimed to provide a process for increasing the sugar contentof immature citrous fruits while in storage.

This concentration has no effect on the com- Still other objects of myinvention are the provision of means for increasing the ratio betweenthe total solid content of the liquid and the acidity thereof.

I have found that citrous fruit may be colored in substantially shortertime than has heretofore been the case by treating the fruit with a gasof the ethylene series containing a small proportion of ammonia. Itappears that ammonia acts somewhat in the nature of a catalyst toincrease the speed of the reaction brought about by the ethylene.

For example, I have treated green limes from the same lot with ethylenealone and with ethylene .in combination with a small proportion ofammonia, the concentration of ethylene being greater than one part to1000 parts of air, in the region of one part to 10,000 and at atemperature of about 70 F. Those limes treated with ethylene and ammoniadeveloped a satisfactory color in about seven days, whereas thosetreated 'with ethylene alone required ten days to properly color.

It will be noted that the time required for coloring will vary somewhatwith various factors, such as the length of time the fruit has been ofithe trees, and the degree of maturity of the fruit, but the above timerequired for coloring fairly well indicates the general superiority of amixture of ethylene and ammonia for this purpose.

I have also discovered that in citrous fruits, contrary to the teachingsof the prior art, the concentration of ethylene must be increased toconcentrations greater than one part to 1000 before ripening of thefruit will be brought about. I do not attempt to explain the reason whythis should be the case but my investigations have shown me that if theconcentration of the gas is increased to one part in 500 ripening andcoloring of green citrous fruit readilyoccurs. I have also found thatthe time required for the ripening process is materially shortened ifammonia or ammonia producing compounds be added to the gases in smallamounts. It appears from my investigations that ammonia and any othercompound which, under the conditions of the process, will liberateammonia with no ill efiects upon the reaction, may be used to acceleratethe ripening process. It will, of course, be necessary that thecompounds so used be gaseous or capable of being vaporized and mixedwith the gas in order to be presented to the fruit, such for example asmethylamine. While I do not know, I am led to believe that theaccelerating action of ammonia is due to its hydrolyzing effect upon thefruit. Acetylene and propylene may be used in the place of ethylene toaccomplish the ripeningthough ethylene appears to produce a betterflavor in the fruit than the former. Propylene appears to produce thebest flavor but is too expensive at the present time for use in thisconnection. My invention is used for the purpose of coloring fruit bysubjecting the fruit to a mixture of ethylene and ammonia, the ammoniabeing present in relatively small quantities. With the exception of thecomposition the treatment may becarried out in the usual manner byintermittently subjecting the same to the coloring reagent until ripe,the

. usual precautions with respect to temperature and of ethylene gasequal in volume to one part in 300 to 800 parts of air, the exactproportion depending upon the character, the condition, or maturity ofthe fruit. The gases are permitted to mix inthe chamber and I may or maynot add a small proportion of ammonia or methylamine, only a tracethereof being necessary. The temperature of the treatment rooms ismaintained preferably between 65 and F. It is also advisable to maintainthe humidity of the gasesat a point high enough to prevent drying andshriveling of the fruit. I permit the fruit to remain in contact withthe gaseous mixture for approximately twenty-four hours, and then openthe chamber to permit the fruit to be aired. Ethylene is then againliberated into air of the chamber. This intermittent airing is not anessential part of the process but I have found that under cer--tainconditions better results are obtained if The fruit is tested formaturity according to the rules and regulations of the citrous fruit lawof the State of Florida. While I have referred to the fruit laws ofFlorida, it has been only for purposes of illustration since anysuitable method of test may, be applied for determining the ripeness ofthe fruit, the test outlined being the most common. A Brix hydrometer isused for testing the percent of total solids, a proper temperaturecorrection factor being applied. The acidity is found by titrating 25cc. of the juice against an NaOH or KOH solution 1.0 cc. of which isequivalent to 10 milligrams of anhydrous'citrous acid. Phenolphthaleinis used as the indicator. The percentage of acid may then be calculatedfrom the total quantity of material present. The ratio days dependingupon the maturity and condition of the fruit. 1

Example 0. 1.Normal grapefruit, green in color,'hard, and having noaroma, was treated for seven days with a concentration of one part ofethylene to 500 parts of=air.' A trace of ammonia was added. At the endof the third day the fruit was yellow and had the aroma characteristicof ripe grapefruit. At the end of seven days the fruit met therequirements of the State of Florida maturity test.

Before Fruit treated Untreated treatment with 0 H; fruit check Solids7.8 s. 9 s. 00 Temp. correct .20 .20 .20 Percent total solid 8. 00 9. l08. 20 Percent acid 1.53 l. 38 1. 49

Ratio 5. 29 to 1 6. 59 to 1 5 50 to l The minimum ratio for maturitywith total solids of 9.1 is 6.45 to 1. The untreated fruit columnindicates what happened to fruit held for a like period under likeconditions as the treated fruit when no ethylene was used.

Example No. 2.-A second test exactly duplicating Example No. 1 exceptthat the ammonia was' Before Treated gliated treatment fruit check .208.80 8.00 1. 41 6.98tol 5.67t01 Minimum ratio for maturity with totalsolids of 8.8 is 6.7 to 1.

Example No. 4.Abnormal fruit suffering from a rust disease was treatedat a concentration of one part of gas to- 400 parts air for ten days.

Minimum ratio for maturity with total solids of 8.95 is 6.6 to 1.

Fruit which is not quite mature may be caused to meet the requirementsof the maturity test by treating it with a concentration of about onepart of ethylene to 700 parts of air for about three days. The number ofdays required for this treatmentwill, of course, vary according to thestage ,of maturity of the fruit being treated. Though the examples showthe results of the treatment of grapefruit the process is equallyapplicable to all citrous fruits, even limes being ripened with equalfacility.

Attention is directedto the fact that I have provided a process formaterially increasing the rate of coloring of fruits over thatheretofore 'known wherein a small percentage of ammonia is added to agas of the ethylene series to produce a coloring and ripening agentcapable of bringing about the coloring in a materially shorter period oftime. I have also produced a new composition or reagent for thetreatmentof fruits for the purpose of ripening and coloring the samewhich consists of a mixture of a gas of the ethyl--. ene series such asethylene with a small proportion .of ammonia, or ammonia producingcompound, which, when liberated in the atmosphere containing the fruitto produce certain ranges of concentration, bring about'either thecoloring or the ripening of the fruit.

It will be seen that one phase of my invention depends for its successupon increasing the concentration of -ethylene beyond that previouslyused in the coloring of fruits. It has heretofore been considered highlydetrimental to the quality of the resulting fruit to employ a greaterconcentration of ethylene than one-part in 1000. This concentration,however, has been entirely ineffectual in causing citrous fruits toripen. If, however, the concentration is increased to one part in 700,the sugar content of the fruit is gradually increased and the aciditythereof noticeably decreased. The time required for the treatthe fruit.

ment varies greatly depending upon the condition of the fruit and thetemperature. Not only is the composition changed but also the color andthe aroma.

It will be seen that by the use of my process citrous fruits normallyfalling from trees too heavily loaded which have heretofore beendiscarded, a total loss, may be artificially ripened and prepared forhuman consumption. A considerable saving in time is effected sincecitrous fruits generally reach their full size about three months beforematurity and may be removed from the trees, treated by my improvedprocess, and marketed.

It will, of course, be understood that the concentration and the time oftreatment must be varied considerably within the limits set forthdepending upon the condition of the particular fruit being treated.

I am aware that numerous changes and alterations may be made in myprocess as outlined above Without materially departing from the spiritand scope of the invention asset forth in the appended claims but I donot desire to limit them except as required by the prior art.

I claim:

1. A process for ripening citrous fruits comprising subjecting theimmature fruit to the action of an unsaturated hydrocarbon gas, inconcentration greater than one part in 1000 parts fruit. a

2. A process for ripening citrous fruits comprising subjecting theimmature fruit to the action of an unsaturated hydrocarbon gas at ofair, to increase the solid to acid ratio of the temperatures between 60and 80 F., in concentration greater than one part in 1000 parts of air,to increase the solid to said ratio of the fruit.

3. A process for ripening citrous fruits comprising subjecting the-fruitto the action of a gas of the ethylene series in concentrations greaterthan one part in 1000 parts of air, for a period of time dependent uponthe maturity of 4. A process for ripening citrous fruits com- "prisingsubjecting the fruit to the action of a gas of the ethylene series inconcentrations greater than one part in 1000 parts of air at atemperature between 60 and 80 F., for a period of time dependent uponthe maturity of the fruit.

' 5. In the ripening of citrous'fruits, the process of increasing theratio of solid to acid which includes intermittently subjecting thefruit to the action of ethylene gas in concentrations between about onepart in 300 and one part in 800 of air, until the solid to acid ratio ofthe fruit reaches or exceeds a'predetermined figure.

6. A process for ripening citrous fruits comprising subjecting the fruitto the action of ethylene gas in concentrations between about one partin 300 and one part in 800 of air at a temperature between 60 and 80 F.,until the solid to acid ratio of the fruit' reaches or exceeds apredetermined figure.'

'7. A process for ripening citrous fruits comprising intermittentlysubjecting the fruit in a closed container, until ripe, to a gas of theethylene series in concentrations between 'one part ylen'e series inconcentrations between one part in 300 and one part in 800 of air at atemperature of above F., and adding a small quantity of ammonia.

9. A process for ripening grapefruit comprising intermittentlysubjecting thefruit in a closed container, until ripe, to a gas of theethylene series in concentrations between one part in 300 and one partin 800, and adding a small quantity of ammonia.

10. The process of ripening citrous fruits which includes increasing theratio of solid to acid by treating the fruit with a gas of the ethyleneseries in concentrations between about one part in 300 and one part in800 of air, for a period of time dependent upon the maturity of thefruit.

11. The process of ripening grapefruit which includes increasing theratio of solid to acid by treating the fruit with a gas of the ethyleneseries in concentrations between about one part in 300 and one part in800 of air, for a period of time dependent upon the maturity of thefruit.

12. A process for treating citrous fruits to mature the same comprisingintermittently subjecting the fruit until ripe to a mixture of a smallquantity of ammonia with a gas of the ethylene series inconcentration-between about one part in 300 and one part in 800 of air.

13. A composition for the treatment of citrous fruits comprising amixture-of a small proportion of ammonia with a gas of the ethyleneseries.

14. A process for treating citrous fruits comprising intermittentlysubjecting the fruit until colored to amixture of air with a reagentcomprising a small quantity of ammonia and a gas of the ethylene series.

15. A process for treating citrous fruits to color the same comprisingintermittently subjecting the fruit until colored to a mixture of asmall quantity of ammonia with a. gas of the ethylene series inconcentration less than about one part in 1000 parts of air. 7

16. A process for coloring citrous fruits comprising intermittentlysubjecting the fruit until colored to a gaseous mixture consistingofair, a gas of the ethylene series, and a small proportion of ammonia.

17. A process for coloring citrus fruits which comprises subjecting themuntil colored to a mixture of air with a reagent comprising ammonia anda gas of the ethylene series.

18. A process of accelerating the production of the natural ripe colorof citrus fruit comprising subjecting the citrus fruit to the action ofammonia in gaseous form.

19. The process of producing a deeper maturer material coloring uponcolored areas of the rinds of mature and immature citrus fruit,comprising confining the citrus fruit in a closed chamber,

then introducing into the chamber into contact with the fruit a quantityof ammonia in gaseous form.

20. A coloring process for accelerating the production of the naturalripe color of citrus fruit,

for use in conjunction with and simultaneously with a conventionaldegreening process, comprising subjecting citrus fruit to the action ofammonia in the gaseous form at prevailing pressure and temperature.

HELEN REA RUTLEDGE.

